1. Field of the Invention
The present invention is related to an apparatus for measuring flexural waves and/or flexural vibrations using a magnetostrictive sensor and the method thereof, which, in particular, disposes the bias magnet configuration to form the magnetic field around ferromagnetic materials and measures flexural waves and/or flexural vibrations from the time-varying change of the magnetic field in ferromagnetic materials resulting from the Inverse Magnetostrictive Effect.
2. Background of the Related Art
When a ferromagnetic material is subjected to a mechanical force, the internal magnetic status of the material changes, which is called the Inverse Magnesotrictive Effect or the Villari Effect. This is the inverse phenomenon of the Joule Effect, where a ferromagnetic object in a magnetic field, undergoes its dimensional change according to the direction of the magnetic field.
The magnetostrictive sensor (Mss) is ordinarily used as a measuring means of elastic waves based on the Inverse Magnetostrictive Effect. The magnetostrictive sensor (Mss), operating in accordance with the Inverse Magnetostrictive Effect or Villari Effect, has a unique possibility of applications, for it can measure the occurring stress change without any mechanical contact with the objects to be measured, especially for the non-destructive examination, impact test for automobiles, noise pattern measuring, instant modal test, etc.
FIG. 1 is a drawing that illustrates the prior art of the measuring apparatus or method of flexural waves using the magnetostrictive sensor. A beam or other mechanical element 2 is disposed within an insulator 4, and a pick-up coil 3 is placed thereon. A magnet 1 is placed in proximity to one side of the insulator 4 and the pick-up coil 3. Coil 3 connects to an amplifier 7, which amplifies the signal through the coil for an oscilloscope 8. Finally, the signal is sent to a personal computer 9 for signal analysis.
Previously, longitudinal waves and torsional waves could be measured with a magnetostrictive sensor. Thereafter, the method to measure the flexural wave by changing the disposition of the bias magnet has been suggested. But in this case the sensor output was too small to conduct the accurate measurement.
The present invention was devised to solve the above said problems of the prior art, and has the purpose of producing an appropriate apparatus or method to measure the flexural wave using a magnetostrictive sensor, wherein high-sensitive output is obtained, accurate measurement is possible, the manufacture of sensor is simple, and the adjustment of the sensor efficiency is easy.